Lithium-ion battery maintenance

[y_p_w]

Originally Posted By: JHZR2
Li-ion batteries that are not in a single cell configuration can have issues with long term storage at low states of charge. Batteries need to be topped, the highest cells pulled down via resistive load, and the weaker cells charged further up to become "balanced". This is important for the life and wellbeing of large batteries, and is generally built in to a battery management system. Balancing chargers are attempting to do this...

I think even single-cell batteries (like with cell phones) can suffer from deep discharge. Certainly the case if one was left alone for 20 years.

The most important thing is that the charger needs to know specific details about the battery, like the estimated capacity, cycles, etc. I don't know if there's such a thing as a universal charger, although I know of some laptop computers that are equipped for multiple battery types that just drop in to the battery compartment.

 

[JHZR2]

Originally Posted By: y_p_w
Originally Posted By: JHZR2
Li-ion batteries that are not in a single cell configuration can have issues with long term storage at low states of charge. Batteries need to be topped, the highest cells pulled down via resistive load, and the weaker cells charged further up to become "balanced". This is important for the life and wellbeing of large batteries, and is generally built in to a battery management system. Balancing chargers are attempting to do this...

I think even single-cell batteries (like with cell phones) can suffer from deep discharge. Certainly the case if one was left alone for 20 years.

The most important thing is that the charger needs to know specific details about the battery, like the estimated capacity, cycles, etc. I don't know if there's such a thing as a universal charger, although I know of some laptop computers that are equipped for multiple battery types that just drop in to the battery compartment.


Certainly a single cell can self-discharge. Thing is, it can go to zero volts, no more. In various configurations, cells can go into reversal, which is very dangerous.

Any Li-ion going below 2V also dissolves copper from the current collector, which can cause plating and internal shorts.

The point I was making is, a single cell is always intrinsically balanced. Multiple cells only have the total summed voltage, so the charger is intrinsically fooled into thinking a pack is charged, when it may have a high and a low cell. So if you have more than one, you can and will have imbalance, which is why you need to resistively balance for proper performance and life.

 

[y_p_w]

Originally Posted By: JHZR2
The point I was making is, a single cell is always intrinsically balanced. Multiple cells only have the total summed voltage, so the charger is intrinsically fooled into thinking a pack is charged, when it may have a high and a low cell. So if you have more than one, you can and will have imbalance, which is why you need to resistively balance for proper performance and life.

That should be the case for any multi-cell battery unit. I remember hearing that Toyota used 5-cell NiMH packs for their hybrids where each pack was considered separately for charging, and I always wondered how they handle imbalanced batteries in a pack. I won't use anything to charge my AA/AAA NiMH batteries other than something that charges each one individually.